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Date: Tue, 23 Mar 2010 12:22:57 -0500 (CDT) From: Christoph Lameter <cl@...ux-foundation.org> To: Mel Gorman <mel@....ul.ie> cc: Andrew Morton <akpm@...ux-foundation.org>, Andrea Arcangeli <aarcange@...hat.com>, Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>, David Rientjes <rientjes@...gle.com>, Minchan Kim <minchan.kim@...il.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH 02/11] mm,migration: Do not try to migrate unmapped anonymous pages On Tue, 23 Mar 2010, Mel Gorman wrote: > diff --git a/mm/migrate.c b/mm/migrate.c > index 98eaaf2..6eb1efe 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -603,6 +603,19 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, > */ > if (PageAnon(page)) { > rcu_read_lock(); > + > + /* > + * If the page has no mappings any more, just bail. An > + * unmapped anon page is likely to be freed soon but worse, > + * it's possible its anon_vma disappeared between when > + * the page was isolated and when we reached here while > + * the RCU lock was not held > + */ > + if (!page_mapcount(page)) { > + rcu_read_unlock(); > + goto uncharge; > + } > + > rcu_locked = 1; > anon_vma = page_anon_vma(page); > atomic_inc(&anon_vma->migrate_refcount); A way to make this simpler would be to move "rcu_locked = 1" before the if statement and then do if (!page_mapcount(page)) goto rcu_unlock; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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